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TMS320F28069: Question on Sensorless FOC Solution for BLDC Motors

Louis Zhu
Expert 1685 points
Part Number: TMS320F28069

Since aerospace projects require the verification of each line of source code, we have to write our own code instead of using InstaSpin-FOC APIs for our motor control projects. I've been able to come up with a sensor-less FOC solution to drive a PMSM based pump, however, I'm having difficulty in reusing the code to control a BLDC motor based pump. I've run in open loop with reference Vq = 0.2 PU, on TI's DRV8302-HC-EVM platform with different types of motor, and captured phase current waveforms as shown below. You can see that the PMSM motor delivers sinusoidal waveforms, while the BLDC motor delivers sinusoidal plus harmonics due to the mismatch between the sinusoidal drive and back EMF. Without filtering the harmonics, I could not close the current loop. Adding LPF I could close the current loop, and achieved stable estimation of motor position and speed, however, I failed to close the speed loop with the estimated motor position and speed.

Here, I'd like to get your advice on what special care is needed when applying sensor-less FOC algorithm in controlling a BLDC motor. Thank you very much in advance.

  • 0
    TI__Guru** 114520 points
    InstaSPIN-FOC estimates the motor rotor position angle based on motor bemf, so the waveform you attached are right if the position is close loop.
    Did the lab2a or lab2c run well using the BLDC? And got correct motor parameters? The motor can run well if you can identify right parameters of the BLDC used lab02a or lab02c.
  • 0 in reply to Yanming Luo
    Expert 1685 points

    Thank you, Yanming, for your response.
    The waveforms were captured when the motor was running in open loop, but the waveforms are similar when the motor is running in closed loops. However, the controllable speed range is small without knowing the actual motor parameters, because the pump supplier gives pump parameters only. I will use TI's labs to characterize the motor parameters.